Television displays and other types of displays often receive a data stream that is decoded by a decoder. For cost reasons, such decoders often possess inadequate resolution for high resolution displays. For example, eight bit decoders may be utilized where twelve or fourteen bit decoders would be more desirable.
This problem of inadequate bit resolution is exacerbated by other processing steps used in digital light processing systems. For example, to account for the non-linear response of a cathode ray tube, television signal images traditionally have a non-linear transfer function applied, and the non-linear response is provided as the input signal. This non-linear function is referred to as a gamma correction curve. In linear devices such as Digital Light Processing (DLP) Systems available from Texas Instruments, however, a de-gamma function must be applied to the incoming pixel stream to correct the unneeded gamma correction. The de-gamma function requires high input and output precision to prevent contouring. Contouring is a quantization artifact that appears as discreet jumps in smoothly varying images.
Other processing steps further exacerbate the problem of inadequate bit resolution. For example, a dynamic aperture approach has been suggested to reduce dither noise in DLP systems. With dynamic aperture, dark scenes are detected, lamp light output is reduced using an aperture, and incoming data is gained according to the amount of lamp light attenuation. The dynamic aperture approach dynamically adjusts the precision of the DLP System. More precision is added for dark scenes, where dither noises are more perceptible than for bright scenes. The dynamic aperture approach also dynamically adjusts the contrast of the projector. When the lamp light output is reduced, the black level is also decreased. This increase in DMD™ precision and projector contrast further exacerbates contours resulting in inadequate input bit precision.